Sea of Thieves: Anniversary Edition disappeared + my birthdate got set wrong

This seems to be a two pronged issue: A little over three years ago I purchased Sea of Thieves. I am not 100% sure, but I think that was also the time I set up a Microsoft account, as I never had a reason to use one before. I also never had a reason to use one after (until between March and May this year, when I played games on an Xbox of a friend of mine and signed up there to have my own progresses saved), except for playing Sea of Thieves, why I am sure this is the account I used back then, in a period I played the game again a little while ago, and wanted to use it again now. Unfortunately the game just disappeared from my Microsoft account, I can´t find it in the store and can´t install it anymore. While searching for it in my account I also realized my birthdate is set to xx.xx.2019, which is 31 years younger than I actually am. As I read on the Sea of Thieves Website that one needs to have a Microsoft account with a legal age over 18 I have a feeling this is why the game got removed from my account. I still have the Paypal receipt of my purchase of Sea of Thieves and unfortunately no clue as to how to get to play the game again like this and would be very appreciative of your help. Thank you.

:)